- Site selection and markup
- Pit and drainage
- Reinforcement and slab filling
- Bowl waterproofing and insulation
- Connection of embedded equipment
- Backfilling of soil
- Bowl and side trim
A pool with a concrete bowl according to the manufacturing technology is akin to a buried strip foundation, standing on a monolithic slab. Differences: loads on the walls (at the pool they fall on tension) and a high level of waterproofing, regardless of the nature of the groundwater.
Site selection and markup
The place for the future pool is chosen not only based on the size of the bowl..
It is necessary to take into account the possibility of supplying engineering communications:
- Water pipes. It is prohibited to take water for the pool from open sources; it must come from a central or autonomous water supply system.
- Sewerage. If there is a central sewerage system, “waste” water is discharged into it. If the site is equipped with an autonomous sewage system, then you should not overload the septic tank with almost pure water from the pool, in this case, use a drainage well (absorption or storage). It is not recommended to use water for irrigation due to treatment with chlorine and algicide.
- Electricity is necessary for the operation of technological equipment and illumination of the bowl (if provided).
Another recommended condition is the absence of closely growing trees. They serve as one of the sources of biological water pollution..
The easiest way to start the markup is to draw the center line of the future pool (usually the correct geometric shape is chosen for the bowl). On the most axial, the length of the pit is marked, and from these points the width is “beaten off”.
The dimensions of the pit are taken with a margin of 0.5-1.5 m (depending on the type of soil). This “gap” is necessary for the installation of the formwork, and after concreting and removing the shields – for the external waterproofing of the pool.
Also, near the pool, it is necessary to provide a place for a room (or caisson) for placing technological equipment. In addition to the pump, filters and shut-off valves, a boiler and a heat exchanger for heating water can be placed here..
Pit and drainage
Before digging a pit, you need to decide on the height of the side of the future pool (it depends, among other things, on the terrain). And already from the upper edge of the side, the depth of the pit is counted taking into account the thickness of the bottom plate, cladding and cushion.
For a pillow, 30 cm of two equal layers of crushed stone and sand is usually enough, but for weak soils, crushed stone is added with a thicker layer.
The pit is dug to the calculated depth. For loose soil, the walls are made with a slight slope and, in order to avoid shedding the soil, they are strengthened with shields. The bottom of the pit is leveled and tamped.
Trenches for drainage pipes are being dug along the perimeter of the future slab. The distance between the pipes and the wall is chosen based on the wall thickness, therefore, in this case, they retreat from the edge of the slab 25-30 cm (based on the wall thickness of the pool).
The pipes should lie with a slight slope towards the drainage well, the depth of which is laid 1 m lower than the lowest point of the pit.
The pipes are wrapped with geotextiles and laid in a trench on a layer of rubble. Then they fill the trenches with rubble and start forming the “cake” of the pillow under the bottom slab.
First, a layer of crushed stone of fine or medium fraction is poured. Then a layer of sand is poured, poured with water and rammed a pillow.
Next are two layers of roll waterproofing. The strips of the first layer are covered with an overlap of 15–20 cm, and the strips of the second layer are shifted relative to the first by half the width of the roll. Seams are poured with hot bitumen or sealed with a gas burner.
Sheets must extend beyond the dimensions of the pool. The size of the outlet should be enough to cover the thickness of the slab and reach the walls of the pool, and this is at least 30 cm.
Then the formwork is installed to pour the slab.
Reinforcement and slab filling
Calculating the thickness of the slab and the parameters of the armored belt is a rather difficult engineering task. There is a simple, practical approach that experience has shown to give a fairly reliable result:
- If the side length of the bearing reinforced concrete structure exceeds 3 m, then the diameter of the reinforcement bar must be at least 12 mm. And usually the pool has at least one side more than 3 m.
- Reinforcement is carried out with two nets. The distance between them should be at least 70 mm, and to the surface of the slab – 50 mm on each side. This allows the thickness to be calculated. For example, for reinforcement 12 mm: 4 x 12 + 70 + 2 x 50 = 218 mm, and for 16 mm – 234 mm. Round up in multiples of 50 and get 250 mm.
- The mesh size of the mesh is chosen 20×20 cm. And from the standard ratio of the cross-sectional area of the reinforcement at the cut to the cross-section of the structure, equal to 0.001, the diameter of the reinforcement is chosen.
- Even for a pool length of 10 m, the calculation shows that the strength of a slab 250 mm thick, with a reinforcement diameter of 12 mm and two armored belt meshes with a cell of 20 cm, will be more than sufficient.
When reinforcing the perimeter of the slab, it is necessary to provide for the outlets of the rods above the surface. They will then be used to bind the armored belt of the pool walls. There are two options:
- use rods bent at an angle of 90 °, which are knitted with an overlap to the upper and lower mesh (for the inner and outer reinforcing mesh of the walls);
- put U- or U-shaped brackets from reinforcement.
The second option is preferable.
The same staples are used to tie the meshes at the ends of the slab, and they should not reach the edge of the slab by the same 50 mm.
After the slab is reinforced, the bottom drain is laid (at the lowest point of the pool, at a distance of 0.5-1 m from the wall) and a pipe is brought to it.
Pouring of concrete is carried out in one step, without long breaks between portions and with guaranteed parameters of the solution itself. Therefore, it is better to use ready-made concrete of class B15 and brand W4 (waterproof).
Before the walls are erected, the slabs are given time to gain sufficient strength. It takes from 4 to 7 days (depending on the presence of additives in the concrete).
Pool wall construction technology is standard for monolithic construction:
- knitting a reinforcing cage from two meshes;
- installation of embedded elements of the water supply system;
- installation of wall passages for embedded elements;
- assembly of formwork, strengthening it with struts and ties;
- pouring concrete.
Here it is also necessary to use reinforcement with a diameter of at least 12 mm. Unlike a strip foundation, the load on the walls of the pool will fall not on compression, but on tension, and in this case, the main part of the pressure is taken by the rods located horizontally. Therefore, the restriction for the minimum diameter of reinforcement with a length of more than three meters comes into force..
Bowl waterproofing and insulation
After the concrete has matured, the formwork is removed from the walls and the external and internal waterproofing of the pool is made..
External waterproofing. Work begins with cleaning the surface of soil particles, paying special attention to the base of the bottom plate. A bituminous primer is applied to the ends of the slab and walls and pasted over with two layers of roll waterproofing. First, the sheets protruding from under the slab are folded up and glued. Then, from the bottom up, the walls are pasted over with overlapping strips, with an offset of the seams between the layers. At the same time, carefully processing the surface of the walls around the wall passages of the embedded elements.
Internal waterproofing is performed with moisture-resistant coating or plastering solutions based on Portland cement and hydrophobic additives. They do it in two layers: rough (using a reinforcing mesh) and finishing. And here, special attention is paid to the treatment of the surface of the walls around the embedded elements, as well as the joint between the bottom plate and the walls..
To maintain a comfortable water temperature, spend less energy on heating it and extend the season of pool operation, it is necessary to insulate its walls. This is best done with two layers of extruded polystyrene foam (which also has good waterproofing properties).
Connection of embedded equipment
Before backfilling, it is necessary not only to connect the embedded equipment (skimmer, nozzles, drain), but also to ensure the tightness of the connection of the wall passages to the pipes that go into the technological room.
Backfilling of soil
Backfilling of the sinuses around the pool walls is usually done with excavated soil. But this is if the soils are not heaving.
For heaving soils, the backfill is carried out by mixing sand into the soil, or using only sand. This compensates for wall pressure from the ground in winter and improves drainage of sediment water during the rest of the year..
Bowl and side trim
The interior decoration of the bowl is usually done with ceramic or glass tiles. Mosaic tiles can also be used, but there will be more work with moisture-resistant grouting.
As an option, there is also pasting the inner surface of the bowl with PVC film.
The cladding of the outer, visible part of the pool walls and sides can be made with other materials. For example, decking or natural stone tiles.